Process requirements for high temperature and high pressure valve castings

The working environment of valve castings for petrochemical industry has the characteristics of high temperature, high pressure and hydrogen (including hydrogen sulfide). Its pressure is generally 14 ~ 25 MPa, and the temperature of reaction system is up to about 400 ℃. These characteristics require that valve castings must be made of high-strength, wear-resistant and corrosion-resistant materials, and the castings must not have casting defects such as inclusions, slag inclusions, pores, shrinkage porosity and cracks.

ZHY casting has organized technological breakthrough and adopted advanced casting and smelting technology. The valve castings manufactured by ZHY casting fully meet the requirements of customers.

1. Requirements for chemical composition and mechanical properties of cf8c

CSiMnSPCrNiMoNb
≤0.08≤2.00≤1.50≤0.015≤0.02018.0-21.09.0-12.0≤0.508XC-1.00
Note: the content of Nb is 1 ~ 8 times that of C

Cf8c chemical composition requirements and mechanical property requirements (ASTMA351) are shown in Table 1 and table 2.

Rm/MPaReL/MPaALo/%
≥485≥205≥30

2. Metallographic examination

Metallographic structure and erosion test shall be carried out one by one. The test shall be carried out according to astme381, and the inclusion level shall meet the requirements of Table 3; Segregation and banded uneven structure with size larger than grade 2.5 in ASTM E45 standard are not allowed; The ferrite content is 4% ~ 16%.

Sulfide (A)Silicate (B)Alumina (C)Spheroidized oxide (D)Total number of levels
≤ grade 1.0≤ grade 1.5≤ grade 1.0≤ grade 2≤ grade 5

3. Intergranular corrosion detection

The sensitized intergranular corrosion test shall be carried out one by one, and the test method and test results shall meet the requirements of ASTM a262 e method.

4. Nondestructive testing

4.1 Radiographic testing

100% radiographic testing shall be carried out one by one, and the testing range shall comply with ASME B16 34. The test method shall be carried out according to MSS sp54 standard, and the test results shall meet the following requirements: porosity / shrinkage casting defects, not less than grade 2; Others, not allowed.

4.2 Liquid penetrant testing

100% liquid penetrant testing shall be carried out one by one according to ASTM e165 standard, and the test results shall meet the following requirements: ① the length of any linearly displayed casting defect shall not be greater than 2 mm; ② The size of single circular casting defect shall not be greater than 4 mm; ③ The cumulative length of dense casting defects (refers to concentrated defects with size less than 0.5 mm) is within any 100 mm × Not more than 2 mm in an area of 100 mm.

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